In the Atlantic Ocean, locating a right whale the size of a school bus can be like finding a needle in a haystack. But a new generation of sharp-eared underwater robots can pinpoint the leviathans' locations in real time. Armed with acoustic equipment and onboard computers, these "gliders" hear singing whales and alert humans so shipping traffic can avoid the mammals—and so scientists know where to find them.

Last month, two 6-foot-long (1.8-meter-long), torpedo-shaped robots from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts used digital acoustic monitoring equipment to detect 9 North Atlantic right whales (Eubalaena glacialis) in the Gulf of Maine—the first-ever detection of baleen whales from these types of autonomous vehicles.

"Recording the sound creates a spectrogram, which to a scientist is almost like a sheet of music that visually represents the sounds you're hearing," explained WHOI researcher Mark Baumgartner.

The gliders process and classify these acoustic signatures, then surface every two hours and transmit evidence of whale calls to shore-based computers while the animals are still nearby. "We can use this information to very quickly draw a circle on the map and say, hey, we know there are whales in this area, let's be careful about our activities here. The government can then alert mariners and ask them to reduce their speed and post a lookout."

Ship collisions are a major source of mortality for the critically endangered right whales, and account for perhaps a third of all known deaths. Devastated by whaling, the species has been slow to recover: Less than 500 individual right whales remain, and biologists stress that each living animal's survival is important for the future of the species. (Read an article about right whales in National Geographic magazine.)

Biologist Regina Asmutis-Silvia, of Massachusetts-based WDC, Whale and Dolphin Conservation, has worked for years on whale strikes, entanglements, and other conservation hazards. She said the gliders have terrific potential and will be an extremely useful tool for both science and conservation.

"But, like anything else, it does have its limitations," she cautioned. "From a conservation perspective the limitation is that right whales aren't vocalizing all the time. So if you're not hearing them, it doesn't mean they're not there," she said.

"That system works fantastically," Baumgartner said. "But it's moored in one place and [our gliders] can move, so this is another step in the direction of having autonomous systems that can remotely detect animals."

The robots' acoustic system is also very flexible. While currently armed with data to detect right, humpback, fin, and sei whales, new sounds and species could be added that would enable the gliders to travel widely in search of other marine creatures.

The gliders can work at sea for four or five weeks before their batteries need recharging. If money and management priorities allowed, one could imagine a fleet of such vessels someday cruising constantly and collecting valuable data on whales and other marine animals.

The underwater robots boast a suite of environmental sensors to record temperature and salinity, and to estimate algae population levels at the base of the marine food chain. "They even have an instrument that gives us a crude sense of how much of the zooplankton that right whales feed on is in the area," Baumgartner said. "So they have an enormous capacity to help us understand not only where the whales are, but why they are there." (Related: "Right Whales Return to Former Killing Ground.")

But for both conservation and science, the importance of simply finding the whales in the first place can't be overstated. Traditional spotting methods, overseen by NOAA, employ observers on ships and airplanes. They have advantages but are expensive and they don't always work, especially when weather and seas are rough.

"I've worked on a number of projects where we just had great difficulty even finding the animals," Baumgartner said. "So it's a great feeling to have a capability like this that gives us some advance notice. Before we left the dock we knew that right, humpback, and fin whales were in our study area—and when we got there that's exactly what we found."